An experimental investigation into electromyography, constitutive relationship and morphology of crucian carp for biomechanical “digital fish”

Abstract

Currently, the integrated biomechanical studies on fish locomotion come into focus, so it is urgent to provide reliable and systematic experimental results, and to establish a biomechanical “digital fish” database for some typical fish species. Accordingly, based on the control framework of “Neural Control — Active Contraction of Muscle — Passive Deformation”, the electromyography (EMG) signals, the mechanical properties and the constitutive relationship of skin, muscle, and body trunk, as well as morphological parameters of crucian carp, are investigated with experiments, from which a simplified database of biomechanical “digital fish” is established. First, the EMG signals from three lateral superficial red muscles of crucian carp, which was evolving in the C-start movement, were acquired with a self-designing amplifier. The modes of muscle activity were also investigated. Secondly, the Young’s modulus and the reduced relaxation function of crucian carp’s skin and muscle were determined by failure tests and relaxation tests in uniaxial tensile ways, respectively. Viscoelastic models were adopted to deduce the constitutive relationship. The mechanical properties and the angular stiffness of different sites on the crucian carp’s body trunk were obtained with dynamic bending experiments, where a self-designing dynamic bending test machine was employed. The conclusion was drawn regarding the body trunk of crucian carp under dynamic bending deformation as an approximate elastomer. According to the above experimental results, a possible benefit of body effective stiffness increasing with a little energy dissipation was discussed. Thirdly, the distribution of geometric parameters and weight parameters for a single experimental individual and multiple individuals of crucian carp was studied with experiments. Finally, considering all the above results, generic experimental data were obtained by normalization, and a preliminary biomechanical “digital fish” database for crucian carp was established.